Continuous video stream playback systems using MPEG and variants are well known in the art. With improvements in memory subsystems and digital content delivery methods, higher continuous video images, such as those using the HDTV/ATSC 1920x1800i format will become more common.
A continuous moving video image stream in its raw form requires very high transmission rates. One way of limiting by the high transmission rates is currently solved by using compression schemes, such as MPEG encoding schemes, that take advantage of continuity in inter-frame content to create very highly packed data. MPEG and similar variants use motion estimation of blocks of image data between frames to perform this compression.
The step to compress video data is processor and memory bandwidth intensive. Motion estimation, a compression step, requires a large amount of the computational work that can use up a significant amount of available bandwidth. In Motion Estimation, a frame of image data is first subdivided into a plurality of fragments or blocks. Next, a fragment or group of blocks of the current frame image is compared against one or more fragments or group of blocks in another frame or frames. The optimal fragment or group of blocks in each of the alternate frames may not be in the same location as the current frame. This location is often different between each of the alternate frame or frames and the current frame. The location of each of these fragments is represented as a motion vector of the form (+/−Dx, +/−Dy).
In the case of MPEG, each of Dx and Dy is a multiple of 0.5. A motion vector that has a 0.5 component means that the fragment from an alternate frame is formed by averaging two side by side pixels from either the same horizontal row or vertical column or four pixels in a 2×2 block. A complex processor and memory bandwidth intensive search algorithm that has to consider a plurality of fragments combinations is generally used to construct each motion vector.
With extremely high resolutions, such as the 1920x1080i format, the data rate of such a compressed stream will be very high. This high data rate poses at least three sets of problems. First, to record or save such a stream over any length of time requires large amounts of storage that can be prohibitively expensive. Second, many display devices that can be used to view such a stream may not be capable of displaying such a high resolution data stream. Third, where there is a data network with multiple viewing or receiving devices, such a network will typically have a fixed bandwidth or capacity. Such a network may be physically incapable of simultaneously supporting multiple viewing devices.
Note, that in general, there can be a plurality of motion vectors required to build each fragment or macroblock of a frame. This further adds to the processing and bandwidth problem. Accordingly, there is a need for an improved device and method for processing video streams.